There are numerous methods for manufacturing gear wheels. In the case of chipping soft pre-machining, one differentiates hobbing, gear shaping, generating planing, and power skiving. Hobbing and power skiving are so-called continuous methods, as explained in greater detail hereafter.
This relates to the chipping machining of crown wheels. In conjunction with the disclosure herein, a crown wheel is considered to be a gearwheel, whose main body has a ring shape or disk shape and in which teeth are arranged in the region of one front side. Therefore, such gear wheels are sometimes also referred to as face gears in English. Such crown wheels are also distinguished in that they can be paired with a regular spur gear as a pinion.
A crown wheel, as used herein, has a face angle that, in the case of pairs that are not axially offset, corresponds to the axis angle between the axis of rotation of the crown wheel and the axis of rotation of the paired gearwheel pinion.
If the face angle of the crown wheel is 90°, such a gearwheel is also referred to as a planar face wheel.
A good overview of the already known methods for producing crown wheels can be inferred from the PCT application WO 2011/017301 A1. Further exemplary tools and methods are already known from the following documents: EP 0699114B1, DBP 1074366, and U.S. Pat. No. 2,308,891.
The two documents DBP 1074366 and U.S. Pat. No. 2,308,891 relate to methods for power skiving crown wheels. Heretofore, tools that have a shape like a cutting wheel have been used in power skiving. Such a tool is arranged axially-offset to the crown wheel in the case of power skiving, in order to thus generate the cutting components required for the chip-removing method kinematically. The tool is moved over the entire tooth width to form a tooth of the crown wheel. There are various movement approaches in this context.
It is a general requirement in this case to design the tool and the movement of the tool such that the desired tooth profile is generated in a sufficient tolerance at all points along the tooth width of the tooth of the crown wheel. The problem arises in this case due to the changing engagement angle over the tooth width together with the required axial offset of the tool. Since the tooth flank, for example, must extend radially in the case of a straight-toothed crown wheel, and since an engaging pinion has tooth flanks that extend parallel to its own pinion axis, it results from the intercept theorem that the engagement angle on the tooth flanks of the crown wheel must decrease from the outside to the inside.
The axial offset of the pair of pinion and crown wheel typically does not correspond to the axial offset of tool and crown wheel during the production.
For the mentioned reasons, only approximate solutions result in the case of the production of the tooth flanks on the crown wheel.
In addition, it is significant that the cutting conditions can change strongly from the outside to the inside (in relation to the workpiece) upon the use of a tool like a cutting wheel.